"Doubled" appended custom shapes
The armature itself doesn't store all the bone shapes ('Custom Object' in 2.8+), it just references them (or the bones do). This means that when you append an armature that is using custom bone shapes it has to append the objects that are being used as the custom bone shapes as well. So what you are seeing is the armature and the custom shape objects it's referencing.

If you're in 2.79 you can just move the bone shape objects to a new layer or if you're in 2.8 you can move them to a new collection and hide them.